1. Technical Field
This invention relates generally to methods, systems and apparatus for managing digital communications systems.
2. Description of Related Art
Digital subscriber line (DSL) technologies provide potentially large bandwidth for digital communication over existing telephone subscriber lines (referred to as loops and/or the copper plant). In particular, DSL systems can adjust to the characteristics of the subscriber line by using a discrete multitone (DMT) line code that assigns a number of bits to each tone (or sub-carrier), which can be adjusted to channel conditions as determined during training and initialization of the modems (typically transceivers that function as both transmitters and receivers) at each end of the subscriber line.
Vectored DSL systems can increase data rate performance by eliminating or reducing crosstalk effects within twisted pairs that belong to the vectored system. In two-sided vectored DSL systems, a number of twisted pairs (also referred to as “loops” and/or “lines”) are grouped together, and are used to transmit a single stream of information. In this case, the transceivers of all lines are physically co-located, and they may even share the same hardware or software. Vectoring effectively applies joint signal processing techniques at the transmitters, at the receivers, and/or at both sides.
Two-sided systems are considered to be “single-user” systems, because there is a single information source and a single information sink, despite the multiplicity of lines. In one-sided vectored DSL systems, distinct information streams are transmitted over the lines that comprise the system. Downstream vectoring basically applies transmitter precoding to the signals to be transmitted on the lines, and upstream vectoring similarly applies joint decoding to the signals received on the lines. In such systems, there are as many information sources (and sinks) as there are lines, and the transceivers typically are separated geographically at the customer side (the CPE side). Each line is considered to be a distinct “user” in this case.
In some DSL deployment cases, some customers may use a single line while other customers use multiple (bonded) lines. However, earlier systems have been unable to combine the features of one-sided and two-sided vectored systems, meaning that these hybrid systems have had to forego the benefits of vectoring. In those cases, applying vectoring simultaneously to all lines (both bonded and non-bonded lines) would provide significant performance benefits.
Systems, apparatus, methods and techniques that enable simultaneous vectoring over bonded and non-bonded lines would represent a significant advancement in the art. More specifically, systems, apparatus, methods and techniques for implementing such vectoring over bonded and non-bonded lines would represent a significant advancement in the art.